As a commercial value of fruit and vegetables and flowers, freshness is the most important factor. However, the fruit and vegetables and the flowers are perishable due to decomposition gas such as ethylene gas, ammonia gas, or acetaldehyde that is released from themselves and induces decomposition. For this reason, there is a problem that after-ripening, softening, or tarnishing progresses with the lapse of time, whereby freshness declines and a commercial value sharply decreases.
For example, with respect to a cut flower out of flowers, withering of floral leaves or falling of buds easily occurs due to generation of ethylene gas. In addition, by decay of vase water or stems or clogging of stems with chemical substances or bacteria, water absorption is suppressed and withering of leaves or flowers is likely to occur.
In order to suppress such deterioration of freshness, for example, a method for facilitating water absorption using a surfactant (ion-based), a method for acidifying vase water with a sulfate, a nitrate, or an aluminum sulfate and using the acidified water as an antibacterial agent or a bacteriostatic agent, and a method for suppressing generation of ethylene gas using a silver thiosulfate have been known from the related art. In these methods, however, it is difficult for general users to handle chemicals to be used, because concentration management of the chemicals is hard, heavy metals are contained in the chemicals, or the chemicals are very expensive.
Under such circumstances, a freshness retaining agent (gas purification agent) is desired which is handled with ease and has gas purification action to suppress an adverse effect to be caused by decomposition gas, thereby being capable of retaining freshness of fruit and vegetables or flowers over a long period of time. As such a freshness retaining agent, there has been proposed a freshness retaining agent using a carbon-based material such as bamboo charcoal or wood charcoal which is a familiar material originated from a natural product and has excellent adsorption performance of gas.
For example, as a freshness retaining agent of the related art, there is a freshness retaining paper for vegetables and the like (see PTL 1) which is formed by coating a mixture obtained by kneading a styrene-acrylic copolymer binder with charcoal powders on a stored article facing side of an easily disintegrable/moisture-proof/waterproof paper and has easily disintegrable/moisture-proof/waterproof and decomposition gas adsorption performance, wherein the styrene-acrylic copolymer binder is obtained by a hydrosol method and adjustment of a glass transition temperature in a range of 65 to 75° C., and the easily disintegrable/moisture-proof/waterproof paper is formed by being dried at a temperature of the minimum film forming temperature (MFT) or higher.
In addition, a wet-type gel deodorant has also been proposed. For example, there is a gel deodorant in which a carbon-based adsorbent such as activated charcoal, wood charcoal, or bamboo charcoal or a silica-based adsorbent is dispersed into a gel (see PTL 2). Further, there is also a gel antibacterial deodorant in which an adsorbent selected from powder of activated charcoal, Bincho-charcoal, bamboo charcoal, or wood charcoal and a plant antibacterial component are dispersed into a gel (see PTL 3).